<!DOCTYPE html>
<!-- fieldset with one valid element and you dynamically add a barred constraint
validation element -->
<html>
  <head>
    <style>
      fieldset:valid { display:none }
    </style>
    <script>
      function onLoadHandler()
      {
        document.getElementById("fieldset").appendChild(document.getElementById('i'));
        document.documentElement.className='';
      }
    </script>
  </head>
  <body onload='onLoadHandler();'>
    <input id='i' value='foo' readonly>
    <fieldset id="fieldset" id="fieldset">
      <input id='j' value='bar' required>
    </fieldset>
  </body>
</html>
